Sources and Generation Parameters of the Hydrocarbon Background of Bottom Sediments in Small Estuaries of the Tatar Strait

Abstract

The paper presents data on the composition of organic matter (OM) in the surface layer of bottom sediments (BS) in two small estuaries in the southwestern part of the Tatar Strait (as of summer of 2014 and 2016). The concentration of hydrocarbons (HC) varied from 0.01 to 2.0 mg/g. The HC content in the uniform silt–psammite sediments (0.55–1.47 mg/g) was higher than the biogenic background level (≈0.1 mg/g). The percentage of HC carbon of total Corg (TOC) in the sediments of Muchke Lake (2.68% on average) was much higher than that in Toki Lake and than the value of ≤1% assumed as an indicator of the absence of a hydrocarbon load. The percentage of autochthonous OM (determined from the chlorophyll a content) in the sediments of weakly flowing Muchke Lake is 41% of TOC, and the value for flowing Toki Lake is 18%. The data obtained in the course of this study are consistent with the molecular composition of the n-alkanes: the OM of Muchke Lake is dominated by that of hydrobiont origin, whereas the OM of Toki Lake consists mostly of terrigenous–humic compounds. The n-alkanes contain much compounds typically produced by bacterial synthesis, which indicates that microorganisms played an important role in forming the hydrocarbon background of sediments in the small estuaries.